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Planetary roller screw classification

Views:13     Author:Site Editor     Publish Time: 2021-02-05      Origin:Site

Planetary roller screws are classified into: roller non-circulating type (RGT series and RGTB series) and roller circulating type (RGTR series). At the same time, reverse planetary roller screws (RGTI series) can also be provided. The lead accuracy is divided into two levels: KL5=±0.005mm, KL10 (standard)=±0.01mm. (315mm stroke)

1. RGT series and RGTB series

RGT series and RGTB series planetary roller screws are mainly composed of main screws, nuts and rollers.

RGT and RGTB series acyclic

The main screw is a multi-head screw (mostly 5-head screw), and the thread tooth profile is triangular. The nut is internal thread, the tooth profile is the same as the main screw. The roller is single-threaded, and the tooth profile is the same as that of the main screw. This ensures that there is no axial displacement between the nut and the roller. The roller is non-circulating.

The side surface of the roller thread is a convex tooth shape, and both ends of the roller are processed into a pinion and a cylindrical optical axis. The cylindrical optical axis is installed and fixed in the end retaining ring hole to keep the equal distance between the rollers. The end retaining ring is floatingly installed in the nut and is axially fixed by the elastic retaining ring.
Pinions at both ends of the rollers mesh with the fixed ring gear inside the nut to ensure that the rollers are axially parallel to achieve the best performance.
Special introduction: Roller non-circulating planetary roller screws are subdivided into RGT series and RGTB series.
The typical differences are:
The nut of the RGT series is composed of two pieces (screws with two-piece cylindrical nut), with a gasket in the middle (Shim).

This structure is very difficult to process, because the middle is a gasket, so the internal thread of the nut is not processed to the end at one time, but is composed of two segments of nut-two segments of thread butt joint. The Swiss GSA company mainly produces this structure, and the product range is very wide: diameter from Φ5mm to Φ245mm, lead from 0.5mm to 50mm; it is also the industry's leading and unique manufacturer.
The nuts of RGTB series are screws with one-piece cylindrical nut. This structure is simpler than RGT. The internal thread of the nut is processed to the end forming at one time, and the difficulty is relatively small. This type of structure is more common.

2. RGTR Series

RGTR series planetary roller screws are composed of main screws, nuts and rollers. The rollers are installed on the roller table and a cage that ensures the distance between the rollers.

RGTR series circulation type

The thread of the main screw is single-end and double-end, and the tooth shape is triangle. The tooth profile of the internal thread of the nut is the same as that of the main screw. When the main screw and the nut rotate, the rollers are axially placed in the nut. For every rotation, the two cams at the end of the nut make each roller return to its original position. Because of its small shape and precise processing, it is mostly used in high-precision positioning occasions such as machine tools. The lead can be designed and calculated as an integer or decimal, and the minimum lead can be made 0.3mm.

3. RGTI Series

The movement principle of the RGTI series planetary roller screw is basically the same as that of the RGT series RGTB series except that the nut system is reversed.

RGTI series reverse screw

The rollers rotate around the main screw (RGT series and RGTB series rotate around the nut), and the rollers move axially within the stroke length of the nut. In addition to the threaded section engaged with the roller on the main screw, the other shaft ends can also be optical shafts or special shafts (for example, anti-rotation). The nut length will be longer than the actual stroke required by the customer, and will be much longer than the nut length of the RGT series and RGTB series, so the RGTI series will be limited by the stroke length.

The range includes: diameter from Φ5mm to Φ245mm, lead from 0.5mm to 50mm.

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